LIC-09-0088, Request for Use of an Alternate Depth Sizing Qualification

Request for Use of an Alternate Depth Sizing Qualification

ML093030358
Person / Time
Site:	Fort Calhoun
Issue date:	10/30/2009
From:	Clemens R Omaha Public Power District
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LIC-09-0088
Download: ML093030358 (6)

Text

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UPPU 0mI", Pub/It: POWIf' O/slrlct 444 South J6h Street Mall Omaha, NE 68102-2247 October 30, 2009 LlC-09-0088 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

Reference:

Docket No. 50-285

SUBJECT:

Request for Use of an Alternate Depth Sizing Qualification Pursuant to 10 CFR 50.55a(g)(5)(iii), the Omaha Public Power District (OPPD) requests approval for use of an alternate depth sizing qualification on the Fort Calhoun Station (FCS), Unit No.1 reactor pressure vessel (RPV) nozzle-to-safe end dissimilar metal (DM) welds from the inside surface.

OPPD will perform volumetric examinations on RPV nozzle-to-safe end DM welds from the inside surface utilizing the ultrasonic (UT) examination technique for a Materials Reliability Program (MRP-139) inspection during the refueling outage beginning November 1, 2009. These examinations are scheduled to be performed again for a 10-year reactor vessel inservice inspection at the end of the current interval in 2013. OPPD requests approval to implement the NRC approved alternative requirements of Code Case N-695 as described in Attachment 1. The NRC has approved similar alternatives.

Code Case N-695 requires that examination procedures and personnel demonstrate a flaw depth sizing error of less than 0.125-inch root mean square (RMS). OPPD proposes the use of an alternative RMS depth sizing error that is greater than the 0.125-inch RMS error value stated in Code Case N-695. Approval for use of this alternative criterion will be needed if flaws are detected.

American Society of Mechanical Engineers (ASME), Code Section XI (Appendix VIII),

Code Case N-695, requires that the maximum error for flaw depth measurements, when compared to the true flaw depth, must not exceed 0.125-inch RMS error. The nuclear power industry has attempted to qualify personnel and procedures for examinations performed from the inside surface of DM welds (Supplement 10, Code Case N-69~)

since November 2002. The most recent attempt at achieving the 0.125-inch RMS was in early 2008. This attempt, as well as all previous attempts, did not achieve the required RMS values for personnel or procedures.

Employment with Equal Opportunity

U. S. Nuclear Regulatory Commission LlC-09-0088 Page 2 The difficulties are associated with the surface roughness of the field welds. At this time, achieving a O.125-inch maximum RMS error is impractical. The vendor that OPPD has chosen achieved a O.189-inch RMS in their Supplement 10 (Code Case N-695) performance demonstration.

If you have any questions regarding this submittal, please contact Mr. Bill Hansher at (402) 533-6894.

emens n Manager

~uclear Engineering RPC/BLlmle

Attachment:

Relief Request in Accordance with 10 CFR 50.55a(g)(5)(iii) c: E. E. Collins, NRC Regional Administrator, Region IV L. E. Wilkins, NRC Project Manager J. C. Kirkland, NRC Senior Resident Inspector

LlC-09-0088 Attachment Page 1 RELIEF REQUEST IN ACCORDANCE WITH 10 CFR SO.SSa(g)(S)(iii)

ALTERNATIVE TO THE DEPTH SIZING QUALIFICATION REQUIREMENT OF ASME SECTION XI, SUPPLEMENT 10 FOR PIPING EXAMINATIONS PERFORMED FROM THE INSIDE SURFACE FOR FORT CALHOUN STATION, UNIT NO.1

LlC-09-0088 Attachment Page 2

1.0 ASME Code Components Affected

Code class: 1 System: RC Examination Categories: B-F, Inservice Inspection Program TABLE 1 WELD NUMBERS BY lSI DESIGNATION Nozzle-to-Safe End Weld Item Location Weld Type 1 N1A Outlet Nozzle (0°) MRC-1/01 Shop 2 N2A Inlet Nozzle (60°) MRC-1/18 Shop 3 N2B Inlet Nozzle (120°) MRC-1/30 Shop 4 N1B Outlet Nozzle (180°) MRC-2/01 Shop 5 N2C Inlet Nozzle (240°) MRC-2/18 Shop 6 N2D Inlet Nozzle (300°) MRC-2/30 Shop

2.0 Applicable Code Edition and Addenda

Fort Calhoun Station (FCS) is currently in the fourth 10-year Inservice Inspection (lSI) interval ending in 2013. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) of record for the current 10-year lSI interval isSection XI, 1998 Edition, including Addenda through 2000 (Reference 1).

3.0 Applicable Code Requirement

The examination of Class 1 piping welds are required to be performed using procedures, personnel and equipment qualified to the criteria of the applicable ASME Code,Section XI, Appendix VIII, Supplements. The applicable supplement to this relief is 10, "QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS."

Paragraph 3.2, "Sizing Acceptance Criteria," Subparagraph (b) of Supplement 10, states that the "examination procedures, equipment, and personnel are qualified for depth-sizing when the RMS [rootmean square] error of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.125-inch (3.2mm)."

L1C-09-0088 Attachment Page 3 Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds,Section XI, Division 1," provides alternative requirements to Appendix VIII, Supplement 10. Paragraph 3.3(c) of Code Case N-695 states, "Examination procedures, equipment, and personnel are qualified for depth-sizing when the RMS error of the flaw depth measurements, as compared to the true flaw depths, do not exceed 0.125-in. (3 mm)." Code Case N-695 is unconditionally approved for use through Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1," Revision 15.

1.0 Impracticality of Compliance OPPD will perform volumetric examinations of the FCS reactor pressure vessel (RPV) nozzle-to-safe end dissimilar metal (DM) welds from the inside surface for a Materials Reliability Program (MRP-139) inspection during the Fall 2009 refueling outage beginning November 1, 2009. These examinations are scheduled to be performed again for a 10-year reactor vessel inservice inspection at the end of the current interval. OPPD will implement the NRC approved alternative requirements of Code Case N-695 for the qualification of procedures and personnel for examinations performed during these inspections.

This reHef is submitted due to the impracticality of meeting the required 0.125- inch RMS value required by Code Case N-695. Code Case N-695 requires that qualified procedures and personnel shall demonstrate a flaw depth sizing error less than or equal to 0.125-inch. RMS.

The nuclear power industry has attempted to qualify personnel and procedures for depth sizing examinations performed from the inside surface of dissimilar metal welds (Supplement 10, Code Case N-695) since November 2002. To date, no personnel or procedure has achieved less than or equal to the ASME Code required 0.125-inch RMS error (Reference 2).

The inability of examination procedures to achieve the required RMS value is primarily due to a combination offactorssuch as surface condition, scan access, base materials and the dendritic structure in the welds themselves. The combination of these factors has proven too difficult for procedures and personnel to achieve an RMS value that meet current Code requirements or Code Case N-695.

2.0 Burden Caused by Compliance The most recent attempt at achieving 0.125-inch RMS was in early 2008. This attempt, as well as previous attempts, did not achieve the required RMS values for personnel or procedures.

The qualification attempts have been substantial. The attempts have involved multiple vendors, ultrasonic instruments, personnel and flaw depth sizing methodologies, all of which have been incapable of achieving the 0.125-inch RMS value.

The process of qualification for this type of flaw sizing is well established. The cost and effort involved to perform a successful demonstration is quantifiable when a capable technique is available. However, when a capable technique is not available, the costs and effort required for a successful demonstration cannot be easily quantified.

LI C-09-0088 Attachment Page 4 3.0 Proposed Alternative And Basis for Use Fort Calhoun proposes using an alternative depth-sizing RMS error value greater than the 0.125-inch RMS error value stated in Code Case N-695 for the examination of welds listed in Table 1 of this relief request. Pursuant to 10 CFR 50.55a(g)(5)(iii), relief is requested to use an alternative that will provide an acceptable level of quality and safety.

As an alternative to the required RMS error stated in Code Case N-695 for procedure and personnel depth sizing, Fort Calhoun will add the difference between the required RMS value of 0.125-inch and the actual RMS value achieved by our inspection vendor to the flaw depth as determined during flaw sizing. The inspection vendor chosen has achieved an RMS of 0.189" for Supplement 10 welds.

Applying the difference between the required RMS error and the achieved RMS error to the actual flaw size, will ensure a conservative flaw bounding approach and provide an acceptable level of quality and safety.

4.0 Duration of Proposed Alternative The alternative requirements of this request will be applied for the duration of the Fourth 10-year lSI interval.

5.0 Precedents Similar relief requests have been granted to the following plants:

1. Seabrook Station, "Seabrook Station Unit No.1 Relief Request For Use Of An Alternate Flaw Sizing Methodology for the Second Inservice Inspection Interval (TAC No. MD9785)," dated May 19, 2009 (ML090850504)

2. Exelon Generating Company, LLC, "Braidwood Station, Units 1 and 2 - Relief Request (12R-49) Regarding Inservice Inspection Program Alternative Method (TAC Nos. MD5996 and MD5997)," dated November 8,2007 (ML072760048)

3. Southern Nuclear Operating Company Inc., "Joseph M. Farley Nuclear Plant Unit 1, and Vogtle Electric Generating Plant, Units 1 and 2 - Evaluation of Relief Request ISI-GEN-ALT-06-02," (TAC Nos. MD 2482, MD2483 and MD2484), dated September 29, 2006 (ML062770359) 6.0 References

1. ASME Code,Section XI, 1998 Edition, including Addenda through 2000

2. Letter from EPRI (C. Latiolais) to OPPD (B. Lisowyj) , "Summary of WESDYNElnternational, LLC Supplements 2 & 10 Depth Sizing Results Obtained from the Inside Surface," dated October 27, 2009